Laser feedback noise is a concern in laser printing systems and other systems, such as optical disks, for example, because it affects print quality by causing artifacts. Accordingly, it will be appreciated that it would be highly desirable to eliminate artifacts in laser thermal images caused by the intensity noise of the laser due to reflected light feeding back to the laser cavity.
A variety of methods are used to eliminate the noise, or, at the very least, significantly reduce the noise. One way is to exploit the polarization characteristics of diode lasers. More than 90 percent of the radiation emitted by a diode laser is linearly polarized and passes through a half-wave plate where it rotates by 90.degree.. The rotated beam is transmitted by a beam polarizer to a quarter-wave plate which has a crystalline axis oriented at 45.degree. from the plane of polarization. The quarter-wave plate converts the linearly polarized light into circularly polarized light. The specular reflections are also circularly polarized but with opposite direction, and are extinguished upon their return to the polarizer. While wave plates and polarizers are effective, they are also expensive, difficult to align and diminish the effective power of the laser. Any lost power adversely effects the printing speed which is undesirable. Accordingly, it will be appreciated that it would be highly desirable to eliminate intensity noise of the laser without employing expensive components or components difficult to align. It is also desirable to eliminate intensity noise without sacrificing the available power of the laser.